Radiofrequency lesions produced by handheld temperature controlled probes for use in atrial fibrillation surgery

Objectives: Detailed analysis of the size and shape of lesions produced by handheld radiofrequency ablation devices at open heart surgery has not been reported previously. Methods: Radiofrequency lesions were made from the epicardial surface of the cardiac ventricles in open-chested dogs. The effects of electrode size, electrode temperature and duration of ablation were studied. In a second group of experiments simultaneous multielectrode ablation was performed on the ventricular epicardium after cold cardioplegia. Results: Using it single 12 x 2.5 mm, electrode and a target temperature of 80 degreesC the lesion depth increased from 3.8 +/- 0.9 mm at 15 s, to 6.1 +/- 0.9 nim at 120 s (P = 0.01). Increasing the target temperature from 70 to 90 degreesC (for 60 s) increased lesion depth from 5.0 +/- 1.2 to 5.6 +/- 1.7 min (P = 0.2). There was no difference in depth of lesions with the two electrode widths (4.0 +/- 0.5 mm (large) vs. 3.9 +/- 1.0 mm (small)). Lesions produced using the multielectrode probe (80 degreesC, 60 s) were 30-35 mm long with even penetration into the tissue. The mean depth of these lesions on microscopic sections was 3.9 mm. The mean width was 7.1 mm. Conclusions: Handheld probes can be used to make deep linear lesions in the myocardium. Lesions expand rapidly and are wider than they are deep. A mulitelectrode ablation device allows rapid formation of linear lesions. (C) 2001 Elsevier Science B.V. All rights reserved.